This invention relates generally to a system and method for testing and verifying adequate bond strength attachment of an adhesively bonded attachment component such as a nutplate or the like affixed to a selected substrate. More specifically, this invention relates to a bond strength tester unit and method for quickly and easily testing nutplate bond strength attachment, e.g., to a blind side of a substrate. In particular, this invention relates to a bond strength tester unit for use with an adhesive bonded nutplate of the general type disclosed in U.S. Pat. No. 5,013,391.
In many manufacturing environments, it is necessary or desirable to install components onto a blind or reverse side of a supporting substrate. As one common example, nutplates are well known in the automotive and aerospace industries for use in mounting a threaded nut or the like onto the blind side of a supporting substrate, typically in alignment with an access opening formed in the substrate, to accommodate subsequent reception of a mating fastener component such as a threaded screw or bolt. Such nutplates include a fastener element such as a floating or fixed nut carried by a base which is fastened to the substrate normally by means of one or more rivets extending through rivet ports formed in the substrate adjacent the access opening. Alternately, adhesive mounting techniques have been proposed for adhesively bonding the nutplate base onto the substrate, thereby avoiding the need to form the rivet ports. For optimum bond strength, such adhesive mounting techniques require the nutplate to be pressed against the substrate with a positive force during curing of the adhesive material.
U.S. Pat. No. 5,013,391 discloses a nutplate assembly including a nutplate base adapted for adhesive bonding onto a substrate. A fixture pin is included for drawing and retaining the nutplate base with a positive force in a direction seated firmly against the substrate for the duration of a bonding agent cure time. The fixture pin is accessible through the access opening at a front side of the substrate for convenient post-cure removal or separation from the nutplate.
While such adhesive mounted nutplates of the above-described type, installed at the blind side of a substrate, accommodate quick and easy subsequent assembly with a mating fastener element, problems can arise when the bond strength is inadequate to support a subsequent load during normal use. That is, in the event of nutplate loading with a force exceeding the adhesive bond strength, the nutplate can separate and fall away from the substrate. When this failure mode occurs following normal substrate installation in an arrangement which renders the blind side of the substrate substantially inaccessible, remedial action can require time-consuming and labor-intensive substrate disassembly from adjoining structures, e.g., such as adjacent substrate panels and frame components in an aircraft or the like.
There exists, therefore, a significant need for a system and method for quickly and easily confirming adequate bond strength attachment of a nutplate to a substrate, and for identifying any inadequately bonded nutplates to permit replacement thereof prior to subsequent manufacturing steps rendering the substrate blind side substantially inaccessible. The present invention fulfills these needs and provides further related advantages.